The corpora allata (CA) of insects secrete juvenile hormone (JH) which controls morphogenesis and reproduction. Little information is available on the physiological stimuli which influence the activity of CA via the brain and very little is known about the neurohormonal regulation of CA. The overall objective of this proposal is directed toward understanding the regulation of the neurosecretory centers in the brain and to isolate and identify putative neurohormones which control CA activity. The tobacco hornworm larva will be used for the proposed studies. The specific aims of the proposal are: a) to determine whether sugar intake in the larvae inactivates the allatotropic center and activates the allatohibin center in the brain, b) to investigate whether the sensory stimulus triggered by sugar intake is transduced into a neural or neurohormonal signal to the brain by the stomatogastric nervous system, and c) to establish the morphological correlates of the functional relationship between the stomatogastric nervous system, brain and the CA. Surgical manipulation of the neuroendocrine system in vivo, in vitro methods for analysis of JH synthesis by CA, and cobalt filling techniques to trace the axonal pathways will be employed in these studies. These experiments will provide detailed information on the regulation of CA and pave the way to isolation and chemical identification of putative CA-regulating neurohormones. These studies could have an important bearing on the development of novel chemical methods for the control of insects which affect the health and economy of mankind.